Proc. 15th INA Conf., Bohol, Philippines
J. Nannoplankton Res. 36 (2), 2016, pp.161–171 © 2016 International Nannoplankton Association
ISSN 1210-8049 Printed by The Sheridan Press, USA

161

Late Holocene paleoceanographic changes off south-western
Africa as inferred from coccolithophore assemblages
Jens Weiser*, Karl-Heinz Baumann
FB Geowissenschaften, University Bremen, Postfach 330440, D-28334 Bremen, Germany; *jweiser@uni-bremen.de

Annette Hahn, Matthias Zabel
MARUM Centre for Marine Environmental Sciences, Leobener Str. D-28359 Bremen, Germany
Manuscript received 14th November, 2015; revised manuscript accepted 16th October 2016

Abstract Coccolith occurrences in sediment core GeoB 8323-2, from the Benguela Upwelling System off

south-western Africa, were analysed to reconstruct the temporal changes in surface water conditions, upwelling
intensity and associated productivity during the late Holocene (last 2.25ka BP). Absolute numbers of total
coccolithophores are low throughout the core, reaching a maximum of 320 x 106 coccoliths/gram sediment around
770 years BP. Despite the low abundance of coccoliths, coherent patterns of a changing assemblage composition
can be identified. These suggest a consistent paleoceanographic development of highly variable Late Holocene
environmental change during the last three millennia. Phases of decreased upwelling in the Benguela Upwelling
System are indicated by elevated abundances of Florisphaera profunda alongside reduced occurrence of Coccolithus
pelagicus and C. braarudii from 2.25–2.00ka BP, ~ 1.00ka BP and during the last 200 years, also accompanied by areduced species diversity. Sea surface temperatures estimated with a Gephyrocapsa-based transfer function are in
the order of 18–20°C. These phases are intersected by periods of colder sea surface temperatures of 16–17°C andincreased productivity, as indicated by an opposing trend for the aforementioned species. Given the climatologicaland oceanographical complexity of the area, deciphering a single driving mechanism for these changes provesdifficult. Synchronous changes in the Antarctic sea ice extent, however, give credit to the conceptual model oflatitudinal migration of the westerly wind belt and its interaction with the south-easterly trade winds as an importantdriver for oceanographic changes in the area.

Keywords calcareous nannoplankton, Holocene, nearshore environment, Benguela, paleoceanography, upwelling,sea-surface temperatures

1. Introduction
Paleoecological investigations largely contribute to ourunderstanding of spatial and temporal variability of (marine)
environments as a whole and their linkage with variationsin the climatic systems.
The southern African paleoclimate, the South Atlantic
and the adjacent BUS (Benguela Upwelling System)
have been studied with increasing attention as they are
key parameters for local and global climatic and oceanographical evolution, water mass transfer and the regional
rainfall patterns (e.g. Summerhayes et al. 1995; Weferet al. 1996; Kirst et al. 1999; Rouault et al. 2003; Farmer
et al. 2005). The BUS is one of the most productive regionsin the world’s oceans and one of the five major upwellingareas worldwide (Summerhayes et al. 1995). Here, a linkage of glacial-scale and millennial variability with orbitalparameters has been well established, with the majority ofdata suggesting SSTs (sea surface temperatures) and lessintense upwelling during interglacials as well as continental rainfall varying in phase with summer insolation (e.g.
Partridge et al. 1997; Flores et al. 1999; Shi et al. 2000;
Baumann & Freitag 2004).
Reconstructions for the Holocene are less conclusive,
partially due to the scarcity of adequate climate records andto the apparently highly variable climatic evolution of thisperiod. While a continuous aridification trend in the winterrainfall zone from 9–5.5ka BP, paralleled by decreasing
upwelling intensities in the southern Benguela, was suggested by Weldeab et al. (2013), decreasing Mg/Ca-SST
estimates point to the opposite trend (Kirst et al. 1999).
The latter data indicates a pronounced period of enhanced
upwelling from 8.5–5.5ka BP, with highest SSTs at around
6ka BP. Despite reporting an ongoing aridification trend,
Chase et al. (2009) also named a humid period in the late
Holocene from 4.2 to 3.5ka BP, followed by pronounced
aridity until 0.3ka BP, that coincides with a decreasing
number of sunspots as reported by Solanki et al. (2004).
Based on speleothem data, Sletten et al. (2013) proposed
relatively humid conditions from 4.6–3.3ka BP and from
1.8ka BP to present.
The potential of coccolithophores as a paleoproxy forsurface water conditions such as water temperature andnutrient availability has been well established in the
study area (Giraudeau 1992; Giraudeau & Rogers 1994;
Boeckel & Baumann 2004), partially with emphasis on
upwelling and eddy formation (Winter & Martin 1990) orAgulhas retroflection (Flores et al. 1999). Moreover, studies from different core sites show a good applicability of162

Weiser et al.

coccolithophores as environmental indicators in nearshore
settings (Green et al. 2008; Silva et al. 2008; Guerreiro
et al. 2013; Guerreiro et al. 2013, 2014; Bonomo et al.
2014). Thus, aiming to contribute to the attempts made to
explain the discrepancies in late Holocene oceanographical and climatic reconstructions of the area, we presenthigh resolution data from the coccolithophore assemblage
composition alongside the absolute and relative abundance of individual species, as well as absolute values forreconstructed SSTs.
2. Modern oceanography of the study area
Southern Africa is an area of close juxtaposition of several
major climate components (Figure 1). Encircled by thewarm Indian Ocean and its AC (Agulhas Current) in the
East and the colder South Atlantic with the BC (Benguela
Current) in the West, it is one of the most climatically convoluted regions on Earth. In addition, two opposing windregimes dominate atmospheric circulation in the area: thesouth-easterly trade winds and the westerly wind belt or
westerlies (Chase & Meadows 2007), with the SE-trades
not only being the main driver for upwelling in the southern BUS, but also the main pathway for moisture advection to the large parts of the continent (see Figure 1).
The Agulhas Current is responsible for intense heatand moisture transport from the Indian Ocean into the
Atlantic Ocean and, therefore, directly influences theclimate, especially at the eastern coast of South Africa(Figure 1). It has repeatedly been identified as one of
the key components of global ocean circulation (Gordon
et al. 1992; De Ruitjer et al. 1999; Lutjeharms 2006).

At the southernmost tip of the African continent thesewaters interact with the Benguela Current and Antarctic
Circumpolar Current in a feature known as the Agulhas Retroflection. This retroflection shortcuts every few
months, spawning a large column of warm and salty Indian Ocean water that drifts into the Atlantic, a phenomenon known as Agulhas leakage, creating large scaleeddies called the Agulhas Rings (De Ruitjer et al. 1999).
These have an important impact on the inter-ocean exchange and, therefore, the Atlantic Meridional Overturning Circulation. As pointed out by Biastoch et al.
(2009) this leakage is directly linked to the position andintensity of the Westerlies and can have a significant
effect on the Benguela Current and the Benguela Upwelling area, where the warm waters from the Indian
Ocean effectively caps the water column, weakening the
upwelling intensity.
The cool Benguela Current is the eastern boundary
current in the South Atlantic, flowing equatorward along
the South African and Namibian coast. It is most known
for its immediate relation to the BUS off northern South
Africa and Namibia, which is one of the most productive
regions in the world’s oceans, reaching from Cape Point(34.58°S) in the south to Cape Frio (18.066°S) at the border between Namibia and Angola (Nelson & Hutchings1983). The BC is often divided into the BOC (Benguela
Ocean Current) and a smaller coastal branch, the BCC(Benguela Coastal Current), which shows a weaker mean
northward flow and is more strongly influenced by local
winds, even leading to reversals in the mean flow direction(Fawcett et al. 2008).

Figure 1: Overview illustrating the main components of the oceanic and atmospheric circulation over southern Africa and the core position of core
GeoB 8323-2 in the Namaqualand mudbelt. Modified after Truc et al. (2013) and Chase & Meadows (2007). Colour shading indicates primary rainfall
season and amount (red/white/right: Summer Rainfall Zone [SRZ], blue/black/left: Winter Rainfall Zone [WRZ])

Late Holocene paleoceanographic changes off south-western Africa…

In the Benguela upwelling region (Figure 1), the equatorward component of the south east trade winds is thedriving force for offshore Ekman pumping that maintains
the upwelling up to several hundred kilometres offshore.
Upwelling prevails throughout the year and is also a common feature on the inner shelf. It is, however, enhanced
during the austral summer (Lutjeharms & Stockton 1987;
Summerhayes et al. 1995). Interannual and interdecadal
fluctuations of the upwelling intensity have been linked
to latitudinal shifts in the zone of the austral westerlies.
Not only do they have a direct influence on the Ekman
effect, also but govern the amount of Agulhas intrusions that
may significantly alter the structure of the water column(Hardman-Mountford et al. 2003; Biastoch et al. 2009).
Rouault et al. (2003) emphasized the importance of anomalies in SST, especially off south western Africa, for governing rainfall at coastal as well as more inland regions.
At the southern tip of the BUS, a coast parallel Holocene
mud belt has formed due to the high input of terrigenous
material through the Orange River and, to a limited extend,
smaller, local rivers in eastern South Africa (Figure 1).
Its inner margin lies 1km to 10km offshore, where water
depth in the area varies between 80m and 140m. Given the
rapid accumulation of sediments, it provides a paleoclimatic archive of exceptionally high resolution (Meadowset al. 2002). While the coarse grained fraction of the Orange River sediment load is mainly transported north due
to wave-induced longshore drift at the river mouth, thepresence of a poleward undercurrent facilitates the accumulation of very fine material in the southern part of themudbelt (Mabote et al. 1997; Rogers & Rau 2006; Hahn
et al. 2016). Despite the fact that the mudbelt sediments
are primarily of terrigenous origin, a significant amount ofbiogenic sediment is added due to the presence of a particularly productive upwelling cell in close vicinity to thecore site (e.g. Monteiro & Roychoudhury 2005).
3. Material and methods
Gravity core GeoB 8323-2 was retrieved during Meteor-­
cruise M57/1 from a water depth of 92m at the shelf off
the Olifants River, South Africa (32.0283°S, 18.2035°E).
Its overall length is 285cm and it is composed of homogeneous, dark greenish-grey sandy mud (Schneider & cruise
participants 2003). A hiatus between the sandy base of
GeoB 8323-2 and the overlaying fine-grained sediments
was observed at 227cm (2.25ka). The age model is basedon linear interpolations of five AMS-14C determinations
on marine gastropods calibrated using the OXCAL software (Hahn et al. 2016). Thus, the undisturbed upper
sequence of core GeoB 8323-2 records at least the last
2.25ka, with the core top considered to be of recent age(0ka BP i.e. 1950 A.D.). Mean sedimentation rate wascalculated as 1mm per year for the uppermost 227cm of
the sediment core.
Sample preparation for coccolith counts followed
Andruleit (1996): Between 95mg and 125mg dried bulk

163

sediment were weighed and brought into suspension withbuffered water without further chemical treatment or filtering. Slightly alkaline water was used to prevent coccolith
dissolution. The chosen amount of sediment has provenuseful to ensure representativeness of the sample and, atthe same time, minimised the weighing error. Since small
particles, such as coccoliths, tend to form aggregates,
ultrasonic treatment for 15–45 seconds was necessary inorder to suspend remaining clumps. The suspension wasthen diluted using a rotary splitter so that 1/100 of theoriginal sample material was recovered in a glass beaker. This amount has proven to be adequate for creatinga monolayer of particles. The suspension was vacuum
filtered onto a polycarbonate filter with a pore width of
0.45µm. After drying, about 1cm2 of the filter was cut out
and glued onto SEM stubs and finally sputter-coated witha gold-palladium alloy.
The prepared samples were examined using a ZEISSDSM 940A scanning electron microscope at 2000x magnification, and coccoliths were counted in a known representative area of the sample. Counts range from 80–230
coccoliths per sample. Iterative counting showed, however, that this low abundance is still sufficient for anadequate representation of the assemblage composition.
Coccolith fragments smaller than 50% of the original size
were not counted. The calculation of numbers of coccoliths per gram sediment followed Andruleit (1996):
Coccoliths[No.
g. sed.

[

=

F*C*S
A*W

Where:• F = filter area [mm²]• C = number of counted coccoliths• A = investigated area [mm²]• S = split factor (100)• W = weight of sample (g)For the calculation of SST, a transfer function based on
six morphotypes of Gephyrocapsa was used (Bollmann
et al., 2002; Henderiks & Bollmann, 2004). Therefore,at least 33 coccoliths per sample were counted extra according to the informal terminology given in Bollmann
et al. (1997). Special emphasis was put on the identification of the three temperature-sensitive morphotypes GE,
GC and GO (Gephyrocapsa equatorial, cold, and oligotrophic, respectively). The relative abundances of the six
different morphotypes were calculated without any further
measurement of the coccoliths, and mean SST was calculated using the formula of Bollmann et al. (2002):
MeanSST [°C] = 19.4336 + (0.1161 * %GE)
+ (–0.0560 * %GC) + (0.0806 * %GO).
Species identification is based on the taxonomic guide
published by the International Nannoplankton Association

Figure 2: a) Relative abundances (top) and absolute numbers (bottom) of the coccolithophore species identified in the core. Black line gives absolute numbers, the grey-shaded areas indicate percentage relative
abundance; b) overview of the assemblage composition

164
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Late Holocene paleoceanographic changes off south-western Africa…

(Young et al. 2003) and the electronic guide to the biodiversity and taxonomy of coccolithophores, Nannotax 3(ina.tmsoc.org/Nannotax3/index.html). Differentiation between Coccolithus pelagicus and Coccolithus braarudii ispredominantly based on a 10µm criterion.
4. Results
Absolute numbers of coccoliths are low throughout thecore, reaching a maximum of 320 x 106 coccoliths/gram
sediment (coc/g sed.) around 770yrs. BP, with an averageof 140 x 106coc/g sed (see Figure 2). Preservation can be
described as average at best, possibly due to elevated content of TOC (total organic carbon) in the sediment. Numbers are especially low in the period from 2.25ka BP to
1.40ka BP and only show minor variation in that interval.
Higher, albeit strongly variable, values characterize theperiod after 1.40ka BP to present. Figure 2a shows absolute values and relative abundances of the most dominant
species, with an overview of the assemblage compositionis given in Figure 2b.
The abundances of Gephyrocapsa muellerae and Emiliania huxleyi show a similar pattern to that of the total
numbers. These two species dominate the assemblage, accounting for ~ 30% and 25%, respectively. Their abundances
and absolute numbers vary significantly (from <10 to >80 x
106coc/g sed.) but do not seem to follow a clear trend.
Similarities can moreover be found between Coccolithus braarudii, C. pelagicus and Gephyrocapsa oceanica.
Three intervals of low abundances can be distinguished(2.25–2.00ka BP, around 1.00ka BP and during the last 250
years.) In between, namely between 2.00 and 1.10ka BP
and between 0.80 and 0.25ka BP, these species are moreabundant. This trend seems to be less prominent in therecord of G. oceanica than for the other two species. These
three aforementioned species seem to be anti-­correlated
to Gephyrocapsa ericsonii and F. profunda, which show
maxima from 2.25–2.00ka BP, around 1.00ka BP andduring the last 200 years. The maximum around 1.00ka
BP is especially pronounced for both species. Florisphaera
profunda also shows a distinct increase during the last 250
years, which can only be observed for G. ericsonii to aminor extent. Calcidiscus leptoporus and C. quadriperforatus do not seem to follow any of these trends. They are
fairly rare until 0.80ka BP, followed by a period of higher
abundances with a distinct maximum at 0.20ka BP, anddecrease again after that. Species grouped as ‘others’ aremainly composed of Syracosphaera spp. and only accountfor up to 6% of the assemblage.
Ecological diversity within the coccolithophore assemblage was determined by calculating Shannon-Index H'(see Figure 3d). This reveals two distinct minima around1.00 and 0.10ka BP. Diversity appears to be elevated in
the lowermost part of the core, but is also characterized
by a pronounced minimum at 2.15ka BP. The period from2.00ka BP to 1.25ka BP shows slightly elevated values,
just as the time span between 0.80ka BP and 0.20ka BP.

165

Notably, the last 200 years are marked by a distinct dropfrom the overall highest value to the pronounced minimum mentioned above.
5. Discussion
5.1 SST-variability based on the
coccolithophore assemblage
Absolute values for past SSTs estimated with the Gephyrocapsa-based transfer function point towards a patternof three warm intervals (18–20°C), intersected by twocolder phases (16–17°C, see Figure 4). Absolute values
are however, slightly higher than the modern annual mean
SSTs (15–17°C). This might be due to the distinct seasonality in coccolithophore growth in the area as reported
by Giraudeau et al. (2000) and Romero et al. (2002). The
Gephyrocapsa-genus that the transfer function is based on
especially thrives in austral spring/summer, which might
explain why the estimated absolute temperatures exceed
modern day annual averages.
Relative changes in SSTs can furthermore be inferredfrom the abundances of the cold water adapted C. pelagicus(Okada et al. 1979; Samtleben & Bickert 1990; Samtleben
et al. 1995; Silva et al. 2008) and the warm-water adapted
G. ericsonii (McIntyre & Bé 1967; Cortés et al. 2001;
Baumann & Freitag 2004). These indicate low SSTs from
2.00–1.10ka BP and from 0.80–0.25ka BP, while warmer
waters can be inferred from high abundances of G. ericsonii in between those phases, especially around 1.00ka
BP (Figure 4). The ratio of G. ericsonii over C. pelagicus
moreover reveals a pronounced warm phase towards thecore top, nicely mirroring the result of the SST estimates.
As the core position is well within the Benguela upwelling
region, the lower temperatures can potentially be assigned
to increased upwelling.
5.2 Coccolithophore paleo-productivity
Three of the identified species (C. braarudii, F. profunda
and G. oceanica) are especially useful for the reconstruction of past productivity changes and stratification at thecore site. Coccolithus braarudii and G. oceanica are indicators of high-productivity, with C. braarudii often associated with upwelling conditions (Cachão & Moita 2000;
Parente et al. 2004), while G. oceanica has been found tochange in phase with sedimentary TOC and mirror general surface water productivity (Kinkel et al. 2000; Silva
et al. 2008). Elevated occurrences of F. profunda havebeen reported as indicators of low productivity and well-­stratified waters (Okada et al. 1979; Beaufort 1997; Marino
et al. 2008). Jointly, their absolute numbers and relative
abundances suggest a consistent development regarding
the coccolithophore paleo-productivity similar to the fivephases of varying SSTs before. Until ~ 2.00ka BP upwelling, water mixing and coccolithophore productivity waslow, as indicated by low abundances of C. braarudii andG. oceanica and high abundances of F. profunda (Figure 3).
The following period until 1.10ka BP shows an opposing

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Figure 3: Compilation of the datasets used for estimating productivity and diversity alongside reference datasets: a) abundance of C. braarudii, asa putative indicator of upwelling intensity; b) G. oceanica, as a general productivity-indicator; c) abundance of F. profunda, mirroring water column
stratification; d) ecological diversity of the coccolithophore assemblages, as expressed by the Shannon-Index H'; e) abundance of N. pachyderma(l) from the central BUS, as indicator of upwelling intensity (Farmer et al. 2005); f) abundance of sea-ice diatoms in core JPC-10 from the Antarctic
Peninsula, as an indicator of latitudinal shifts in the westerly wind belt (Etourneau et al. 2013)

pattern for all three species, which indicates increased mixing and productivity.
For the period between 1.10ka BP and 0.80ka BP apronounced change towards more stratified waters can beinferred from the strong increase in abundance of F. profunda, alongside very low numbers of C. braarudii andG. oceanica. Productivity increased again between 0.80
and 0.25ka BP, while conditions similar to the periodaround 1.00ka BP prevailed during the last 250 years.
Although increasing total coccolith numbers generally
suggest rising primary productivity in the upper water column, they may not necessarily always indicate increases in
upwelling intensity. Coccolithophores are known to also
be adapted to less nutrient-rich areas of the open ocean(e.g. Townsend et al. 1994; Van der Wal et al. 1995; Baumann et al. 2005) and are often outcompeted by siliceousorganisms in high-production regimes. This might explain
why the highest overall counts are registered during a phaseof apparent stagnation of the water column (1.1–0.8ka BP).
Bearing this in mind, a significant change in the productivity can still be identified at around 1.50ka BP, from which
point total absolute numbers show constantly higher values
than in the lower part of the sediment core (Figure 2).
The uncertainty regarding the influence of changing
upwelling conditions, and its imprint on the nannofossil
assemblage, might also explain the slightly ambiguous
results of the Shannon-Index H' diversity assessment(Figure 3). The phases of low inferred coccolithophore
productivity show the most monotonous species assemblages; however, a few samples with arguably morediverse assemblages fall within these timeframes as well(e.g. 2.10ka BP and 0.40ka BP).

Late Holocene paleoceanographic changes off south-western Africa…

167

Figure 4: Compilation of the datasets used for SST-reconstruction, alongside reference datasets: a) C. pelagicus as a cold water indicator; b) G. ericsonii
as a warm water indicator; c) results from the Gephyrocapsa-­based SST-transfer function as developed by Bollmann et al. (2002); d) abundance ofN. pachyderma (l) from the central BUS as indicator of upwelling intensity (Farmer et al. 2005); e) abundance of sea-ice diatoms in core JPC-10
from the Antarctic Peninsula, as an indicator of latitudinal shifts in the westerly wind belt (Etourneau et al. 2013)

5.3 Link to continental climate variability
and possible driving mechanisms
As mentioned above, there are two principal mechanismsthat can alter upwelling intensity in the southern BUS.
The first one being the Ekman pumping induced by theequatorward component of the South East trade winds; thesecond being the variability in the strength of the Agulhas
leakage, where a reduced leakage of warm saline water isthought to facilitate the upwelling (Cohen & Tyson 1995;
Schumann et al. 1995; Lund & Curry 2006; Biastoch et al.
2009). As the amount of leakage is linked to the position
and intensity of the westerly wind belt, both the SE-trades
and the Westerlies have to be considered when assessing
the driver behind the observed changes.
Relating the coccolithophore data with other paleoceanographical and paleoclimatological datasets fromthe area is limited by the scarcity of comparable records
that cover this short period of time at a similar resolution.
The data reported by Farmer et al. (2005) on the abundances of N. pachyderma (l) from IODP-site 1084 (central
BUS, 25.51°S, 13.03°E) reveal a good agreement to theobserved changes in upwelling intensity (Figure 3). This
coherence over a relatively large distance and between
different oceanographical settings (inner shelf vs. lower
continental slope) implies a common driving mechanism
where, generally, upwelling intensifies in phase with astrengthening of the SE-trade winds.
As mentioned before, the trade winds are the main
source of moisture in the SRZ (Summer Rainfall Zone)(see Figure 1) of southern Africa (Tyson et al. 2000; Chase& Meadows 2007; Truc et al. 2013). Building on this understanding, Chase et al. (2009) recently published work

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on the nitrogen isotopic composition of rock hyrax middens from the SRZ, establishing this as an approximationfor SE-trade wind intensity. This record does not reveal
any major changes in the investigated interval, except
for the last 250 years. The nitrogen isotopic compositionindicates wetter conditions and therefore a strengtheningof the SE-trades in the same period where more stratified
and warmer waters are indicated by the coccolithophore
assemblage. This mismatch either points to a decouplingof trade wind strength and upwelling intensity for the late
Holocene or the presence of another localized driving
mechanism in the southern BUS.
As an alternative, data on the abundance of sea-ice
diatoms from the Palmer Deep, western Antarctic Peninsula (64.88°S, 64.20°W), presented by Etourneau et al.
(2013), can be used as an indicator for the extent of the
Antarctic sea ice and, therefore, the latitudinal positionof the Westerlies in the late Holocene. Here, a better
correlation with the changing composition of the coccolithophore assemblage can be found. Higher abundances of sea ice diatoms (indicative of a northward
shift in the westerly wind belt) generally coincide withphases of reduced upwelling intensity and warmer SSTs
as inferred from the coccolithophore assemblages here
(see Figure 3, 4). On the one hand, this contradicts the
proposed hypothesis that the Agulhas leakage, as governed by the Westerlies, controls upwelling intensity inthe southern BUS. On the other hand, a clearer pattern
emerges when taking into account that the Southern
Hemisphere Westerlies and the South East Trade Winds
are counteracting atmospheric systems. Weakening of
the one usually results in a greater influence of the other.
Therefore, the aforementioned phases of increased sea
ice presence mean a more northerly position of the westerly wind belt which, in turn, reduces the influence on
the upwelling in the southern BUS. It does not seem toaffect the general trade wind intensity, as the nitrogenisotopic composition does not follow this trend, but does
appear to have a localized effect on the water column
structure in the vicinity of the core site.
6. Conclusion
Changes in the nannofossil assemblage of sediment core
GeoB 8323-2 from the Namaqualand mudbelt allow fora detailed reconstruction of late Holocene oceanographic
changes in the southern Benguela upwelling system.
Throughout the last three millennia, five phases of characteristic environmental conditions can be identified:
1.	2.25 to 2.00ka BP: Upwelling and productivity indicate
species are low in abundance, while a high percentage of F. profunda and results from the SST-transfer
function indicate warm, stratified waters. This coincides with a more northerly inferred position of theWesterlies.
2.	2.00 to 1.10ka BP: The coccolithophore assemblage
shows a distinctly different composition, indicating

cooler, more productive waters. This interpretation isbacked by similar results from the northern BUS, aswell as reduced influence of the Westerlies.
3.	1.10 to 0.70ka BP: A brief episode of warmer, morestratified waters is indicated, coinciding with peaknorthward expansion of the Antarctic Sea Ice and,
therefore, the westerly wind belt.
4.	0.70 to 0.25ka BP: A second phase of cooler waters
is indicated by distinct increases in C. pelagicus andC. braarudii. Increased coccolithophore productivity
is implied by higher amounts of G. oceanica. Moreover, F. profunda is nearly absent from the samples ofthis period, pointing towards more turbulent waters.
5.	0.25ka BP to present: The coccolithophore assemblage implies another period of warmer, more stratified water at the core site. This stands in contrast to
trade wind related data from the continent, as well as
results from the nearby cores as shown by Weldeab
et al. (2013), who presented geochemical and sedimentological indications for cooler SST and stronger
upwelling.
Deciphering a single driving mechanism proves difficult,
as no direct correlation with either of the proposed mechanism can be identified. Bearing in mind the counteracting nature of the two main wind systems, the Westerlies
and SE-trades, the latitudinal changes of the Antarctic
sea ice extent gives credit to the conceptual model of amodulation of upwelling in the southern BUS driven by
the position of the westerly wind belt. As these changes
are, however, not necessarily mirrored in reconstructions of the trade wind intensity, this appears to be a
localized effect.
Acknowledgements
Jeremy Young, Mariem Saavedra, and an anonymous
reviewer are gratefully acknowledged for their constructive comments that significantly improved this manuscript. This work was conducted within the collaborative
project “Regional Archives for Integrated Investigations” (RAiN), which is embedded in the international
research program SPACES (Science Partnership for
the Assessment of Complex Earth System Processes),funded by the German Federal Ministry of Education andResearch (BMBF).
Raw data can be accessed as digital appendix throughthe information system PANGAEA (www.pangaea.de).
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